This invention relates generally to continuously rotating limit switches; and, more particularly, to a switch used in connection with machines having repetitive cycle of operation, in which use this limit switch renders possible the opening and closing of independent circuits at any desired angular position, and keeping these circuits open or closed for practically any desired angular travel.
Switches of the present type have a wide application in programming and time-sequence operations. They are commonly used on power-presses and similar machinery, where a speed change, or even a complete stoppage or reversal of the part or all of the machinery, is required of certain positions of the main drive.
Most of the prior art switches comprise juxtaposed adjustable disc-like cams mounted on and rotatable with a rotating shaft, the lobe or lobes or each cam making contact at various stages of rotation with an independent roller-type contact unit. Quite complex and expensive devices have been developed through the years for adjusting the angular position and angular size of a particular cam lobe.
Examples of the type of switches involving the field of this invention are illustrated in U.S. Pat. No. 2,903,528 granted to E. H. Kuhn assigned to the assignee of the present invention and recent developments, such as those disclosed in U.S. Pat. Nos. 3,465,269 and 3,721,780 granted to R. V. Hendershot and to R. R. Kelly et al, respectively.
Certain prior art devices which provide both timing and dwell features require a plurality of parallel shafts for supporting and adjusting switch components. It will be apparent that efforts to minimize the number of parts will also minimize the adverse affects of improper alignment between the shafts and between the various members, such as cooperating worm gears. Also, a reduction of parts reduces costs, friction and free play of the cooperating elements comprising the switch assembly.
The present invention contemplates the achievement of the various functions of the prior art, but in a relatively simplified device using a minimum of parts, which in turn provide a minimal amount of friction and free play, as well as material reduction of cost.